Duct detectors are a form of a detector mountable to a duct to provide an indication of a characteristic of the fluid flowing in the duct. For example, a duct detector in the form of a smoke detector can be mounted to a heating ventilation air-conditioning (HVAC) duct to detect smoke therein. Such an arrangement can provide an early indication of smoke in the HVAC system thereby enabling the HVAC system to be shut down to prevent smoke from one portion of the building being distributed about the building by the HVAC system.
HVAC ducts are often mounted within difficult working environments in roof spaces and the like. As such, installing duct detectors can be difficult, and the installation of the detector is sometimes compromised due to these difficult working conditions. For example, structure defining an HVAC plenum for dividing and directing flow from a single duct into four separate ducts might be inaccessible, thereby necessitating the installation of four separate detectors on the downstream ducts.
Moreover, duct detectors require maintenance from time to time, meaning that periodically maintenance personnel must return to these difficult working conditions.
UK patent application GB 2347541 describes a duct detector including an inlet and an outlet, which each open into the duct, and an aspirator in the form of a centrifugal blower to draw air from the duct via the inlet and direct the air toward a sensor before it returns to the duct via the outlet. Other duct detectors omit an aspirator and instead rely upon pressure differences between the inlet and the outlet so that flow in the duct drives fluid through the duct detector.
It is an object of the invention to provide an improved duct detector and components therefor, or at least to provide an alternative for those concerned with duct detectors.
It is not admitted that any of the information in this specification is common general knowledge, or that the person skilled in the art could reasonably be expected to have ascertained, understood, regarded it as relevant or combined it in anyway at the priority date.